cache: Fix issue where single missing CSV deletes all
Created by: joelagnel
There's a bug in trappy caching where corruption or removal of single CSVs causes all CSVs to get removed. Fix this and add a test-case to cover it. Also test that only missing items are regenerated.
Change-Id: Iea41c8e0a005515790b580e7f78f06bdd60141a3 Signed-off-by: Joel Fernandes joelaf@google.com